The present invention relates generally to the field of biological stains and particularly to stains employed in blood sample analysis.
In the preparation of biological samples for analysis, certain natural and synthetic dyes have been used to stain tissues, cells, cell components and other microscopical specimens in order to facilitate their examination with the aid of a high-powered microscope. These dyes stain the materials and bring out color differences between cell components and their background or between different parts of the substrate. Stains are thus employed when it is desired to differentiate chromatically one part of a specimen from another. Because of the variation in the composition of the respective parts of the specimen, attempts to completely stain the specimen must include treatment with one or more different dyes, either in the same or separate solutions. For example, blood smears are usually stained by treatment with a methylene blue-eosinate dissolved in methanol, of which Wright's stain is an example. As Wright's stain contains three different types of dyes, i.e., an acid dye, a basic dye, and a neutral dye, cellular elements responsive to the difference in chemical structure are simultaneously stained.
Though stains such as Wright's stain have been used for some time with reasonable accuracy, there has developed an increasing need for stains possessing greater flexibility and sensitivity to slight variations in the pathological condition of the specimen. Particularly in the instance of the acid dyes, a certain lack of discrimination is evident in the failure of the dye to penetrate certain cellular inclusions such as mitochondria and cytoplasmic granules. Also, even when the desired elements are stained, they are often severely damaged or crenated. It is thus difficult to know the actual condition of the specimen, or to accurately diagnose the patient's condition.
With the advance of medical science bringing to attention new maladies possessing more subtle symptoms, greater sensitivity is required in all aspects of analysis. This need is especially felt in the area of microscopic examination, and the preparation of samples therefor.